import sys
input=sys.stdin.readline
INF = int(1e9)
n = int(input())
maps = []
maps.append([INF]*(n+1))
#배열 입력
for i in range(n):
tmp = [INF]+list(map(int,input().split()))
maps.append(tmp)
#비용 초기화
cost = [[0 for _ in range(n+1)] for _ in range(n+1)]
cost[1][1]=0
def cal(a,b):
if a>b:
return 0
else:
return b-a+1
#디피
for i in range(1,n+1):
for j in range(1,n+1):
if j-1==0 and i-1==0:
continue
elif j-1==0:
button2 = cal(maps[i-1][j],maps[i][j]) + cost[i-1][j]
cost[i][j]+=button2
elif i-1==0:
button1 = cal(maps[i][j-1],maps[i][j]) + cost[i][j-1]
cost[i][j]+=button1
else:
button1 = cal(maps[i][j-1],maps[i][j]) + cost[i][j-1]
button2 = cal(maps[i-1][j],maps[i][j]) + cost[i-1][j]
cost[i][j]+=min(button1,button2)
# for i in range(n+1):
# for j in range(n+1):
# print(cost[i][j],end=" ")
# print('')
print(cost[n][n])
